Lab Final Flashcards
1
Q
Green chemistry
A
an approach to chemistry that aims to maximize efficiency and minimize hazardous effects on the environment and human health
2
Q
Where do Emory shuttles get fuel for shuttles?
A
160 tons of fryer oil and grease were collected in 2017 and made into biofuel for Emory’s shuttles
*uses B5
3
Q
Why is B80 used in the cold instead of B100?
A
Diesel is more viscous so it makes more sense to use a lesser proportion of biodiesel when it is cold
4
Q
Chemical composition of fatty acids
A
RC(=O)OH
R: long chain hydrocarbon
5
Q
Why can you not just use animal fats as fuel?
A
They are solids or viscous at room temperature (saturated fats)
Need to make able to flow
6
Q
Unsaturated fatty acids
A
long chains that contain a C=C double bond
7
Q
Is anything a pure saturated fat?
A
Rarely and the kinks make it difficult to pack triglycerides
8
Q
What is the red diamond in old hazard label?
A
Flammability
9
Q
What is the blue diamond in old hazard label?
A
Health
10
Q
What is the white diamond in old hazard label?
A
Special notice
ex: reacts with water in unstable manner
11
Q
What is the yellow diamond in old hazard?
A
Instability/reactivity
12
Q
Comparison of butanol vs. ethanol as fuel
A
Butanol has more carbon chains so more energy produced
Ethanol produces more CO2
13
Q
What was our biodiesel?
A
a methyl-ester
14
Q
Difference between temperature and heat?
A
Temperature is a measure of molecular motion or kinetic energy
Heat is a transfer of thermal energy between two objects due to differences in temperatures
15
Q
Intermolecular forces in methanol
A
hydrogen bonding (oxygen)
dipole-dipole
dispersion
16
Q
Intermolecular forces in canola oil
A
mostly dispersion
some dipole-dipole due to ester groups
17
Q
Heat of combustion units
A
kJ/g
18
Q
How to find heat of combustion?
A
Normally take how many kJ to heat water and divide by grams of biodiesel, etc.
19
Q
Why is biodiesel said to be carbon-neutral although it produces CO2?
A
Since biodiesel is made from rapeseed and not fossil fuels, it is said that the carbon the rapeseed absorbs during its lifetime is equal to the CO2 released
no net addition to the atmosphere
20
Q
Why is the methanol and the canola oil able to mix?
A
the canola oil contains an ester bond that makes it slightly polarized
21
Q
Why is biodiesel less viscous than starting triglyceride?
A
it is a smaller molecule
22
Q
Kinetics
A
applies to the SPEED of a reaction
23
Q
Thermodynamics
A
applies to the EXTENT of a reaction, the concentration of product that has appeared after an unlimited time
24
Q
Fetal hemoglobin
A
More efficient at binding O2
Has a larger K value
25
Beer-lambert equation
A = e*l*c
26
Molar absorbitivity constant
e in Beer's Lambert equation
27
3 ways to stress a system
1. Temperature
2. Concentration
3. Pressure
28
How do you measure concentration through absorbance when equilibrium is dynamic (i.e. there will never be purely products)?
Put in so much of one of the reactants so that the system is essentially driven to completion
29
How do you determine the wavelength to set spectrometer to for an unknown compound?
Look at the peaks of absorbance on scanning setting
30
What should you use as your blank to measure concentration of FeSCN2+ ?
Highest concentration of iron
31
What should you do to calculate concentration when not given much information?
M1V1=M2V2
32
What happens to the amount of acid when base is added?
Amount of acid decreases
33
How to calculate enthalpy when K was calculated at 2 different temperatures?
Van Hoff's Equation
34
What is the gas constant, R?
.008314 kJ/mol
or
8.314 J/mol
35
What happens when you add silver nitrate to an anion?
Often makes a white precipitate
Ag(anion)
36
What is borax?
a slightly soluble salt
37
How to determine K when there are two products?
Formula looks like: K = [A]2[B]
Can use the mol ratio to substitute
Know that for every 1 mol B, there are 2 mols A
K = [A]2[2A]
38
How can we calculate K by titration?
use the known concentration of the acid/base to solve for the concentration we are looking for
39
End point
is when the color changes, indicating the end of the titrant
40
Equivalence point
when the number of moles of acid is equal to the number of moles of base
41
Titration using a mass burette vs. titration using a volumetric burette
same calculations except one using volume and the other uses mass
42
Why do we use different indicators?
Different indicators are sensitive to different pHs
Phenol red is sensitive to ~7
Phenophtalein is sensitive to ~9
43
How do you determine the temperature of a solution if you have to measure its absorbance?
measure the temperature before and after sampling in the spectrometer
44
Why does it not matter how much water is used to move a sample to a flask for titration?
the number of moles of the substance studied will remain the same
45
Why do we not use M1V2=M1V2 with the acid and base for a titration?
This assumes that there is a 1:1 mol ratio between the acid and base which we do not know
46
Amount of titrant needed when solubility increases?
Less soluble = less titrant
More soluble = more titrant
47
What are the units of entropy?
J/K
48
What happens if extra borax was transferred to the flask for titration?
more borate = larger K
larger K = less free energy, since G=-RTln(K)
49
Where is the buffer region of a titration curve?
the flat line leading up to the spike to the equivalence point
at this point there is conjugate acid and conjugate base present
50
If you titrate a weak acid with a strong base, what is true of the equivalence point?
all of the weak acid would have been converted to conjugate base
51
What is true of halfway to the equivalence point?
there are equal amounts of conjugate acid and base
use Henderson-Hasselbach equation...you have a buffer!!
52
Why does Ka decrease as starting pH increases of a titration?
a higher starting pH indicates a weaker acid and therefore it is not as reactive
53
Rate of reaction
speed at which reactants are converted into products
M/s
kinetics
54
What is the central focus of chemical kinetics?
reaction rates
55
If given a graph of concentration vs. time, how do you find the reaction rate?
take the slope
rate = d(concentration)/dt
56
What would result in the rate change being a decrease by a factor of 4?
A reaction is second order with respect to reactant B and B is halved
57
5 factors that affect rate
1. Nature of reactants
2. Temperature
3. Catalyst
4. Concentration of reactants
5. surface area of reactants
58
Effect of surface area on concentration
Greater the surface area, the faster rate of reaction
More particles are exposed to attack by other reactant particles
59
Arrhenius plot
ln(k) vs. 1/T
* use slope to calculate activation energy
* use y-intercept to calculate A
60
How do catalysts work?
New mechanism
Lowers activation energy (resulting increases k)
They increase the rate of both the forward and the reverse reactions
61
Relationship between activation energy and k
inverse relationship
62
Relationship between temperature and k
direct relationship
63
Surface catalyst
a solid that speeds up a reaction between gases
64
What is slope in a first order reaction plot of ln(A) versus time?
slope = -k
65
What is slope in a second order reaction plot of 1/A versus time?
slope = k
66
What is slope in a zero order reaction plot of A versus time?
slope = -k
67
How to determine the reaction order by graphing?
Graph A vs. t, ln(A) vs. t, and 1/A vs. t
* each correspond to a different order respectively
* known as integrated rate laws
68
What is the limitation of the integrated rate laws?
Can only work for a single variable
69
How to rearrange pseudo-rate laws?
flood the system with A, so there is basically no change in A
rate = ko [B]^n
70
What does K observed equal?
ko = K[A]^m
*A is what the system was flooded with
71
Beer's Law Plot
Absorbance vs. Concentration
72
How to determine the molar absorbvitity constant?
use the slope of the Beer's plot
73
Redox process in ionic compounds
there is a complete change in electrons
74
Redox process in covalent compounds
there is a shift in electrons
75
Oxidizing agent
is reduced
gains electrons
76
Reducing agent
is oxidized
looses electrons
77
Oxidation number
a number assigned to a chemical that represents the number of electrons gained or lost (if the number is -)
78
Electromotive force
E cell
the cell voltage or cell potential
*can occur due to flow of electrons between the anode and cathode
79
Anode
where oxidation occurs (loosing electrons)
is denoted on the left in a standard diagram
80
Cathode
where reduction occurs (gaining electrons)
is denoted on the right in a standard diagram
81
Galvanic or voltaic cells
produce electricity as a result of spontaneous reactions
82
Electrolytic cells
non-spontaneous chemical change driven by electricity
83
An Ox and a Red Cat
An Ox: anode = oxidation
Red Cat: cathode = reduction
84
Cats are +
Cathode is positive
85
Why does a voltaic cell work?
the spontaneous reaction occurs as a result of different abilities of materials to give up their electrons
86
Cell voltages
the potential differences between the electrodes
87
The Standard Hydrogen Electrode
an arbitrary 0 chosen to compare potentials of individual electrodes
88
Colors of Manganese in Different Oxidation States
```
+7 = magneta
+6=green (Arnold)
+5=yellow (or blue) (Tina)
+4=clear w/ brown precipitate
+3=pink
+2=clear w/ no precipitate
```
89
What is the relationship between oxidation number and reducing ability?
greater oxidation number = greater reducing agent
a higher oxidation number means that it lost the most electrons, which means that it donated the most to another substance. it did the most reducing
90
When can you compare oxidation number and reducing ability of different substances?
they have to be reducing the same substance
91
What happens if two samples are contaminated in the murder mystery experiment?
the stronger reducing agent (higher oxidation number) will mask the color of the weaker reducing agent
the stronger reducing agent is more reactive
92
Ferromagnetic electron spin
unpaired electron spins from the atoms in the solid (represented by arrows) align with each other within regions called magnetic domains
93
Ferrimagnetic electron spin
within each magnetic there are two spins in different directions
However, they do not cancel out and this leaves a net magnetism
94
Did we use a ferromagnetic or ferrimagnetic substance?
Magnetite is a ferrimagnetic substance
95
Superparamagnetic
the magnetic domains are the particles themselves
all the electrons within a given particular spin in the same direction
*ferrofluids are superparamagnetic and this makes them magnetize and demagnetize more rapidly
96
Why do ferrofluids form peaks?
they are part of a colloidal suspension that always has small waves constantly present on the surface of a ferrofluid
these waves are amplified in the presence of a magnetic field
97
Reaction mechanisms definition
a step-by-step description of actual events (often collisions) in an overall chemical reaction
98
What does every step of a reaction mechanism do?
Alters a molecules geometry, energy, or produces a new molecule
99
Why do trimolecular processes rarely occur?
the probability of 3 molecules colliding at the same time is incredibly rare
100
Order in a rate law for an elementary process
are the same as the stoichiometric coefficients for an elementary process
101
Intermediates
produced in one step and consumed in another
102
Rate determining step
one elementary step is usually slower than all others
103
SN1 mechanism
2 step mechanism
produces an intermediate
1st order reaction
104
SN2 mechanism
1 step mechanism
does not have an intermediate
2nd order reaction
105
Chemical formula of magnetite
Fe3O4
106
Suspension
a heterogenous mixture that has solid particles large enough to settle to the bottom
107
Colloid
a solution that has evenly distributed particles large enough to remain suspended, but do not settle to the bottom
108
Surfactant
a compound that is added to a liquid to lower its surface tension
ex: detergents
109
Hydracids
an acid that does not contain an oxygen
composed of hydrogen and a nonmetallic element
ex: HF
110
Solvolysis Reaction
a substitution reaction where the solvent is a nucleophile
111
Why is a surfactant used in making your ferrofluid?
a surfactant prevents the particles of magnetite from clumping together (agglomerating)
can't have agglomeration because they need to be equally suspended throughout the solution
112
Why are Fe(ii) and Fe(iii) not magnetic?
their electrons move independently of one another and do not contain large regions where the electron spins are alligned
113
In the SN1 reaction experiment, what were the controls? What did they control for?
1. Not heated test tube. Controlled for tert-butyl's natural reaction with ethanol without heating.
2. No alykl halide added. Controlled for the heating effects of ethanol and the indicator
114
3 alkyl halides reactivity with ethanol
3º, 2º, 1º
*decreasing order. 3º is the most reactive
115
Why did only tert-butyl react with the AgNO3?
tert-butyl has an SN1 mechanism, so when the carbocation intermediate is formed, there is a free halide to combine with the silver and form a precipitate
116
3 steps of SN1 reaction
1. Formation of carbocation
2. Nucleophilic addition of alcohol
3. Deprotonate by solvent
117
Why is tert-butyl the most reactive with ethanol
It has a carbocation intermediate that is highly unstable
118
What happens within the atom when it is fluorescing?
Atom gets excited to a higher energy level and then it emits light when it falls from these higher energy levels
119
Who was awarded the nobel prize in chemistry 2008?
Martin Chalfie, Osamu Shimomura, Roger Y. Tsien
120
How are GFPs used in biology?
can be attached to proteins to see if gene splicing/gene expression worked
121
What did Roger Tsien do?
changed the structure of GFP to produce proteins that glowed cyan, blue, and yellow
122
What did Martin Chalfie do?
used GFP to label neurons in C. elegans
123
Who was the first genetically modified primate?
ANDi
statistically very hard to accomplish
124
What is the structure of GFP?
green flourescent protein consists of 238 amino acids folded in the shape of a beer can
the ends of the chain interact in the middle to create the light (chromophore)
125
Fluorescence
lumination that is due to quickly absorbing high energy light and releasing two or more photons
126
Phosphoresence
lumination that occurs more slowly over time
127
Coordination number
the number of ligand atoms that are bonded directly to the central metal ion
128
Geometry
the geometry (shape) of a complex ion depends on the coordination number and nature of the metal ion
129
Ligand atoms
an ion or molecule that binds to a central ion in order to form a coordination complex
130
Donor atoms per ligand
molecules and/or anions with one or more donor atoms that each donate a lone pair of electrons to the metal ion to form a covalent bond.
131
What properties do ligands have?
they are lewis bases
they are able to donate a pair of electrons
132
Monodentate ligands
use one pair of electrons to form one point of attachment to the metal ion
133
Bidentate ligands
use two pairs of electrons to form two points of attachment with the metal ion
*can go up to tetradentate, etc.
134
Asymmetric synthesis and when it is utlized
using chiral reagents, catalysts, and fragments to produce SINGLE enantiomeric configuration
this approach is used when dealing with big biomolecules
135
Chromatographic resolution of enantiomers
requires an optically active (chiral) stationary phase that allows passage of one enantiomer while the other is held up on the column.
applicable when dealing with a small amount of material
136
Resolution by crystallization
*what we did
diastereomer formation followed by product enrichment by the selective crystallization of one diastereomer over the other.
137
What is the blank for the polarimeter?
Water
138
What does Co(en)3 represent?
C6 H24 N6 Co
139
What is the purpose of a solvent/moisture trap in a vacuum filtration?
Capture solvent that could have been sucked into the line, so the solvent does not destroy the pump
140
What is the purpose of hydrogen peroxide in the preparation of Co(en)3 3+?
hydrogen peroxide works as a oxidizing agent
oxidizing Co(ii) to Co(iii)
141
two major safety hazards of the first experiment?
not to come into contact with sodium hydroxide and hydrogen peroxide
142
After the (+) enantiomer was isolated, why did you have to precipitate the iodide salt out of it?
If we dissolved the crystals into the solution, we would have had additional molecules that can rotate light, so we had to isolate the Cobalt from the tartrate
